This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Recently, the use of peroxynitrite (PN) has been advocated as a means of generating high-valent P450 intermediates. This technique has lead to a number of reports that question our understanding of this large family of enzymes. We wish to use EXAFS, paired with M[unreadable]ssbuaer and Raman spectroscopies, to provide a definitive characterization of the P450-PN intermediate.